1. Field of the Invention
The present invention relates to an LCD panel, and more particularly, to a one drop fill (ODF) LCD panel having a light-shielding pattern capable of preventing light leakage through a peripheral region of the LCD panel.
2. Description of the Prior Art
LCD displays have been widely applied to a variety of information products, such as notebook computers and PDAs, since they have advantages of tiny size, low power consumption, and low radiation emission.
Normally, an LCD panel includes a color filter substrate (CF substrate), a thin film transistor substrate (TFT substrate), and a liquid crystal layer positioned between the CF substrate and the TFT substrate. The TFT substrate further includes a plurality of pixel array regions arranged in arrays on the surface, each pixel array region including a TFT and a pixel electrode for controlling spinning angles of liquid crystal molecules such that each pixel can generate different colors and gray scales.
In general, LCD panels can be divided into two types according to methods of filling liquid crystal molecules: vacuum fill LCD and one drop fill (ODF) LCD. In a vacuum fill LCD, the CF substrate and the TFT substrate are combined together with a sealant, and only a hole is kept. Then, liquid crystal molecules are slowly injected into the space between the CF substrate and the TFT substrate by capillarity action. However, this requires a lot of time (ex: several days for assembling a large size LCD) and a great amount of liquid crystal molecules. Therefore, the vacuum fill method is usually applied to fill only small panels with liquid crystal molecules. In an ODF LCD, first, a sealant layer is pasted onto the bordering part of the TFT substrate. Then, liquid crystal molecules are dropped on the central part of a pixel region, and the CF substrate and the TFT substrate are affixed. Finally, an ultraviolet beam is utilized to irradiate the sealant for hardening the sealant such that the CF substrate and the TFT substrate are tightly combined together. In comparison with vacuum fill method, ODF method is more effective (it takes only a few hours to fill a large size LCD), and needs fewer liquid crystal molecules. Hence, at present, the ODF method is normally applied to fill large LCD panels with liquid crystal molecules.
Please refer to FIG. 1. FIG. 1 is a schematic diagram of a conventional ODF LCD panel 10 before substrates are combined together. As shown in FIG. 1, the ODF LCD panel 10 comprises a CF substrate 12, and a TFT substrate 14 positioned in parallel with the CF substrate 12. The ODF LCD panel 10 includes a pixel array region 16 and a sealant region 18. The pixel array region 16 further comprises a plurality of color filters 20 positioned on the surface of the CF substrate 12 corresponding to the TFT substrate 14, a plurality of black matrices 22 positioned between any two neighboring color filters 20, and at least a liquid crystal drop 24 dropped onto the surface of the TFT substrate 14.
Please refer to FIG. 2. FIG. 2 is a schematic diagram of the conventional ODF LCD panel 10 after the CF substrate 12 and the TFT substrate 14 are combined. As shown in FIG. 2, the CF substrate 12 and the TFT substrate 14 are connected by a sealant 30 such that the liquid crystal drop 24 is equally spread in the pixel array region 16 between the CF substrate 12 and the TFT substrate 14. However, since the sealant is a photocuring material, it has to be irradiated by an ultraviolet beam to become completely strengthened so that the CF substrate 12 and the TFT substrate 14 are perfectly affixed and combined together. In addition, if the sealant 30 is not totally hardened, the sealant will react with the liquid crystal molecules so that the efficiency of the liquid crystal molecules will be deteriorated.
Please refer to FIG. 3. FIG. 3 is a top view of the conventional ODF LCD panel 10. As shown in FIG. 3, the pixel array region 16 of the ODF LCD panel 10 comprises a plurality of pixels arranged in arrays, and each pixel includes a thin film transistor (TFT) 34 for controlling switching of each pixel 32. Each pixel 34 includes a gate 36 electrically connected to a scan line 42, a drain electrically connected to a data line 44, and a source 40 electrically connected to a pixel electrode 33. On the other hand, the sealant 18 comprises a plurality of metal conducting wires 26A and 26B. The metal conducting wires 26A and 26B are respectively connected to each scan line 42 and each data line 44 at one end, and are respectively connected to gate driving ICs (not shown) and source driving ICs (not shown) at the other end. In this case, voltage signals of each IC (not shown) can be delivered to the gate 36 and the source 40 of each TFT 34.
As above mentioned, after the ODF LCD panel 10 is combined together, the sealant 30 needs to be irradiated by an ultraviolet beam for completely hardening the sealant 30, so that the CF substrate 12 and the TFT substrate 14 become tightly fixed together. Besides, in this case liquid crystal molecules will not react with the sealant 30 so that the function of liquid crystal is not influenced. However, when the ultraviolet beam irradiates the sealant 30 from the front side of the CF substrate 12, the light source provided by the back light module (not shown) will pass through the gap between the metal conducting wires 26A and 26B in the sealant region 18 so that light leakage occurs in the peripheral region of the ODF LCD panel 10.
To avoid this problem, the ultraviolet beam is then irradiated form the back side of the TFT substrate 14 for hardening the sealant 30, and a black matrix layer (not shown) is installed on the surface of the CF substrate 12 corresponding to the sealant region 18 for preventing from light leakage in conventional technologies. As shown in FIG. 3, however, since the metal conducting wires 26A and 26B are not transparent, the sealant 30 cannot be completely hardened. In this case, display quality is deteriorated.
Therefore, ensuring the sealant of ODF LCD panel is completely irradiated by the ultraviolet beam to avoid light leakage at the bordering part of ODF LCD panel is a key topic for study in designing ODF LCD panels.